Fluoroelastomers and in particular perfluoroelastomers such as those described in “Modern Fluoropolymers”, edited by John Scheirs, Wiley Science 1997, offer excellent protection against high service temperatures and are resistant to a wide variety of chemical reagents. Fluoroelastomers are elastomers prepared by curing a fluoroelastomer precursor (“fluoroelastomer gum”) made from monomers containing one or more atoms of fluorine, or copolymers of such monomers with other monomers, the fluoromonomer(s) being present in the greatest amount by mass. The fluoroelastomer precursor is a fluoropolymer that is suitable to prepare a fluoroelastomer having desired elasticity properties. Typically, the fluoroelastomer precursor is an amorphous fluoropolymer or a fluoropolymer that hardly shows a melting point. When the fluoropolymer has a perfluorinated backbone, a perfluoroelastomer results but also polymers having a partially fluorinated backbone are used.
A commonly used process for the preparation of fluoropolymers is the aqueous emulsion polymerization which offers an environmental advantage over polymerization in solvents. Generally, the aqueous emulsion polymerization of fluorinated monomers is carried out in the presence of a fluorinated surfactant although techniques have also been developed in which no fluorinated surfactant is added to the polymerization.
Fluoroelastomers have been used successfully in a number of applications due to their ability to withstand high temperatures and aggressive chemicals, as well as the ability of the fluoroelastomer gum to be processed using standard elastomer processing equipment. Amongst other, fluoroelastomers have been used in the semiconductor industry in the chip manufacturing process where the fluoroelastomer may be used in seats of chip fabrication equipment. During chip manufacturing, the fluoroelastomer can be exposed to high temperature and aggressive chemicals. While the fluoroelastomers, and in particular perfluoroelastomers have been used in the semiconductor industry, there continues to be a need to improve the fluoroelastomers so as to make them more suitable for this specialized application. In particular, available fluoroelastomer compositions often have a too high amount of ionic components and in particular too high amounts of metal cations, which limits their suitability for use in the chip manufacturing. This is particularly the case if the fluoropolymer that is used to make the fluoroelastomer, was prepared through an aqueous emulsion polymerization process.
It would thus be desirable to find an alternative method for producing high purity fluoropolymers and fluoroelastomers such that they meet the demands of the semiconductor industry and are suitable for use therein.